Issue |
A&A
Volume 441, Number 2, October II 2005
|
|
---|---|---|
Page(s) | 819 - 829 | |
Section | Celestial mechanics and astrometry | |
DOI | https://doi.org/10.1051/0004-6361:20053355 | |
Published online | 19 September 2005 |
On the V-type asteroids outside the Vesta family
I. Interplay of nonlinear secular resonances and the Yarkovsky effect: the cases of 956 Elisa and 809 Lundia
1
IAG, Universidade de São Paulo, São Paulo, SP 05508-900, Brazil e-mail: valerio@astro.iag.usp.br
2
Observatório Nacional, Rio de Janeiro, RJ 20921-400, Brazil e-mail: froig@on.br
3
Southwest Research Institute, Department of Space Studies, Boulder, Colorado 80302, USA e-mail: davidn@boulder.swri.edu
Received:
2
May
2005
Accepted:
22
June
2005
Among the largest objects in the main belt, asteroid 4 Vesta is
unique in showing a basaltic crust. It is also the
biggest member of the Vesta family, which is
supposed to originate from a large cratering event about 1 Gyr
ago (Marzari et al. 1996, A&A, 316, 248). Most
of the members of the Vesta family for which a spectral
classification is available show a V-type spectra. Due to their
characteristic infrared spectrum, V-type asteroids are easily
distinguished. Before the discovery of 1459 Magnya
(Lazzaro et al. 2000, Science, 288, 2033) and of several V-type NEA
(Xu et al. 1995, Icarus, 115, 1), all the known
V-type asteroids were members of the Vesta family.
Recently two V-type asteroids, 809 Lundia and 956 Elisa,
(Florczak et al. 2002, Icarus, 159, 178)
have been discovered well outside the limits
of the family, near the Flora family. We
currently know 22 V-type asteroids outside the family, in
the inner asteroid belt (see
Table 2). In this work we
investigate the possibility that these objects are former family
members that migrated to their current positions via the
interplay of Yarkovsky effect and nonlinear secular resonances.
The main dynamical feature of 956 Elisa and 809 Lundia is that
they are currently inside the (z2 by Milani &
Knežević 1994, Icarus, 107, 219) secular resonance.
Our investigations show that members of the Vesta dynamical family
may drift in three-body and weak secular resonances until
they are captured in the strong z2 secular resonance. Only
asteroids with diameters larger than 16 km can remain in one of
the three-body or secular resonances long enough to reach the
region of the z2 resonance. This two-step mechanism of capture into
the z2 resonance could explain: i) the current resonant orbits of
956 Elisa and 809 Lundia; ii) why their size is significantly
larger than that of the typical member of the Vesta family; and iii)
provide a lower limit on the Vesta family age. We
believe that other V-type asteroids could have followed the
same path, and could currently be inside the z2 resonance.
In an forthcoming article of this series we will investigate the role that
other mechanisms of dynamical mobility, such as close encounters with
massive asteroids, may have played in causing
the current orbital distribution of the remaining 20 other V-type
asteroids.
Key words: minor planets, asteroids / celestial mechanics
© ESO, 2005
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